<!-- 右侧字母 -->
<template>
  <div>
      <ul class="list" >
          <li class='item' v-for="item in letters" :key="item" @click="handleLetterClick" @touchstart.prevent="handleTouchStart" @touchmove="handleTouchMove" @touchEnd="handleTouchEnd" :ref='item'>{{item}}</li>
      </ul>
  </div>
</template>

<script>
export default {
  data () {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    }
  },
  props: {
    cities: Object
  },

  components: {},

  updated () {
    this.startY = this.$refs['A'][0].offsetTop
  },

  computed: {
    letters () {
      var letters = []
      for (var i in this.cities) {
        letters.push(i)
      }
      return letters
    }
  },

  methods: {
    handleLetterClick (e) {
      console.log(e.target.innerText)
      this.$emit('change', e.target.innerText)
    },
    handleTouchStart () {
      this.touchStatus = true
    },

    handleTouchMove (e) {
      if (this.touchStatus) {
        if (this.timer) {
          clearTimeout(this.timer)
        }
        this.timer = setTimeout(() => {
          var touchY = e.touches[0].clientY - 79
          var index = Math.floor((touchY - this.startY) / 20)
          if (index >= 0 && index <= this.letters.length) {
            this.$emit('change', this.letters[index])
          }
        }, 16)
      }
    },

    handleTouchEnd () {
      this.touchStatus = false
    }

  }
}

</script>
<style lang='stylus' scoped>
@import '~styles/varibles.styl'
.list
  display flex
  flex-direction column
  justify-content center
  position absolute
  top 1.58rem
  right 0
  bottom 0
  width .4rem
  .item
    text-align center
    line-height .4rem
    color $bgcolor
    cursor pointer
</style>
